The present invention relates to a device for detecting synchronous errors of high-lift surfaces such as landing flaps or slats on aircraft, comprising an optical conductor which is laid over at least two adjacent high-lift surfaces, a light source and an optical receiver which are allocated to different ends of the optical conductor, as well as an evaluation unit for determining a synchronous error on the basis of the light signal received from the optical receiver.
Usually, in aircraft wings, there are several high-lift surfaces or flaps in the form of slats and/or landing flaps arranged adjacent to one another. These are normally operated synchronously with appropriate flying manoeuvres. If this results in ruptures in the suspension or breakdown or jamming of the control elements of these high-lift surfaces, one or even more of the adjacent high-lift surfaces can no longer be extended to the desired degree. On the one hand, this results in unwanted rolling moments of the aircraft due to asymmetry, on the other hand, in high mechanical stresses of the flap bodies and the remaining intact drive line as well as of the structure of the wing case.
Various detection systems have already been proposed to identify such synchronous errors of the movable high-lift surfaces. According to a first solution, proximity switches or angle sensors detect the extended position of the high-lift flaps on the basis of the kinematics thereof. The synchromism is electronically monitored on the basis of the signals of these sensors. However, sensor systems of this type are constructed in a comparatively complex manner.
Another known detection system for synchronous errors of this type is the so-called lanyard system in which a rope is placed over the span of the wing to be monitored, said rope being fastened to the outer end of the flap body on the outside of the wing and connected with a switch to the flap body on the inside of the wing. When synchronous errors occur, the rope is pulled tight due to the changed length of the built-in area, as a result of which said switch is actuated. Due to the large span of the rope, however, this system does not exhibit a very sensitive response behaviour.
Furthermore, it has already been proposed to detect the aforementioned synchronous errors by a so-called overload detector. The increased friction or blockage caused by the skew in the flap guide releases the corresponding overload safety device of the flap drive system. However, with this system, the drive and the corresponding structural components experience comparatively high mechanical stresses since the system does not respond until the overload is reached.
A device of the aforementioned type is known from EP 1 029 784 B1. An optical fiber cable is led over all of the guiding edges/high-lift surfaces of an aircraft wing and provided for transmitting a light signal generated by a light signal generator on one end of the cable to a light signal detector on the other end of the cable. The optical cable is thereby led at each transition point between two adjacent high-lift surfaces through two control elements which are directly adjacent to one another and belong to various high-lift surfaces. The cable is thereby led through elongated slits in the control elements, so that slight misalignments do not have any effect on the cable. However, if the relative movement between two adjacent high-lift surfaces exceeds the permissible degree of tolerance defined by the elongated slits, the cable is cut by the two control elements sliding past one another, so that the signal transmission is interrupted by the optical conductor cable. The breakdown of the signal at the optical receiver is detected as a synchronous error by the evaluation unit connected therewith. Of course, the disadvantage of this previously known system is the fact that it is already destroyed when synchronous errors occur for the first time and the optical cable must be replaced accordingly. To avoid this, according to a second embodiment described in EP 1 029 784 B1, the cable should have a nominal rupture point in the form of a plug/socket connection between each of the two control elements of the respectively adjacent high-lift surfaces. After the synchronous error which has occurred has been eliminated, the corresponding segments of the optical conductor cable can be reconnected via the plug/socket arrangement. However, this arrangement of plug/socket connections between each pair of control elements on adjacent high-lift surfaces is relatively extensive, in particular in its assembly.